Development And Characterization Of Nanosilica

Silica,namely precipitate SiO2,has the characteristics of high purification, lowdensity, high specific surface area and fine decentralization, and also has high optics andmechanism capability, so it has been widely used in many fields, such as activator carriers,compound materials of macromolecule, electronic encapsulation materials and fineceramic materials. In recent years, silica is more and more used in technology of militaryaffairs, communications, electron and laser.The project systematically discusses the method and technical way of making silicathrough vitriol precipitation method, respectively studies on the influences of theconcentration of water glass, reaction temperature, pH of the solution, time of acid sol-gelreaction and the amount of activator butanol on the making and character of silica bymodern analyzing and testing methods, precisely evaluates the factors influencing themaking, optimizes the making scheme and characterizes its structure, particle size, surfacephysical and chemical characters under such an optimized scheme.Through the research, we find nanosilica is wadding-like precipitation. Analysis ofelectronic diffraction and X-ray diffraction shows that nanosilica is amorphous substance.Under TEM, the particle is spherical with the minimum size of 14 nm and average size ofabout 35 nm. Particles of the silica contact with each other in a linked branch-like way andthe aggregates are linked in a chain branch way with the force of Van Der WaalsInteraction, so the linking is easily broken and reversible. In the experiment, the averagedistance between the atoms measures 7.26A|°, and the range ordering domains from 8 to 11A|°. To a certain extent, the range ordering domains shows the degree of the tightness of theamorphous substance. The narrower the range is, the looser the structure is. The researchon surface characters of silica shows the changing tendency of loss-in-weight rate ofabsorbed water and surface activation energy has a same rule with the changing of particlesize and specific surface area. The smaller the particle size is, the larger the specificsurface area is, the higher the loss-in-weight of absorbed water is, and the lower the surfaceactivation energy is. Through the method of Coats and Redfern, the surface activationenergy of silica measures 35.566kJ/mol. Infrared absorption spectrum analysis shows –OHon the surface of SiO₂ is in the state of being linked with the framework and the surfacestructure of the silica is presumed.Through the process, we also find the concentration of water glass, reactiontemperature, pH of the solution, time of acid sol-gel reaction, the amount of activatorbutanol all have great influence on the making and character of silica.